# mars.tensor.arctan#

mars.tensor.arctan(x, out=None, where=None, **kwargs)[source]#

Trigonometric inverse tangent, element-wise.

The inverse of tan, so that if `y = tan(x)` then `x = arctan(y)`.

Parameters
• x (array_like) –

• out (Tensor, None, or tuple of Tensor and None, optional) – A location into which the result is stored. If provided, it must have a shape that the inputs broadcast to. If not provided or None, a freshly-allocated tensor is returned. A tuple (possible only as a keyword argument) must have length equal to the number of outputs.

• where (array_like, optional) – Values of True indicate to calculate the ufunc at that position, values of False indicate to leave the value in the output alone.

• **kwargs

Returns

out – Out has the same shape as x. Its real part is in `[-pi/2, pi/2]` (`arctan(+/-inf)` returns `+/-pi/2`). It is a scalar if x is a scalar.

Return type

Tensor

`arctan2`

The “four quadrant” arctan of the angle formed by (x, y) and the positive x-axis.

`angle`

Argument of complex values.

Notes

arctan is a multi-valued function: for each x there are infinitely many numbers z such that tan(z) = x. The convention is to return the angle z whose real part lies in [-pi/2, pi/2].

For real-valued input data types, arctan always returns real output. For each value that cannot be expressed as a real number or infinity, it yields `nan` and sets the invalid floating point error flag.

For complex-valued input, arctan is a complex analytic function that has [1j, infj] and [-1j, -infj] as branch cuts, and is continuous from the left on the former and from the right on the latter.

The inverse tangent is also known as atan or tan^{-1}.

References

Abramowitz, M. and Stegun, I. A., Handbook of Mathematical Functions, 10th printing, New York: Dover, 1964, pp. 79. http://www.math.sfu.ca/~cbm/aands/

Examples

We expect the arctan of 0 to be 0, and of 1 to be pi/4: >>> import mars.tensor as mt

```>>> mt.arctan([0, 1]).execute()
array([ 0.        ,  0.78539816])
```
```>>> mt.pi/4
0.78539816339744828
```

Plot arctan:

```>>> import matplotlib.pyplot as plt
>>> x = mt.linspace(-10, 10)
>>> plt.plot(x.execute(), mt.arctan(x).execute())
>>> plt.axis('tight')
>>> plt.show()
```